HTM 03-01 Part A vs Part B: What’s the Difference?

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If you manage estates or ventilation in a healthcare environment, you will hear “Part A” and “Part B” referenced constantly. But the distinction matters, because they serve different purposes, are carried out at different times, and test different things.

Part A: Validation (New or Refurbished Systems)

Part A validation is carried out once: when a new ventilation system is installed, or when an existing system undergoes significant refurbishment. Its purpose is to confirm that the installed system meets its design specification and is fit for clinical use.

When it happens: Before handover to clinical operation.

What is tested:

• Full performance against design specification
• Air change rates and pressure regimes
• HEPA filter integrity
• UCV performance and entrainment
• Recovery rates
• Temperature, humidity, noise, lighting
• Complete documentation review

Who should do it: An independent specialist, not the installing contractor. The installer carries out commissioning; independent validation provides impartial confirmation that the system actually works as specified. See our HTM 03-01 Part A validation service.

Part B: Verification (Ongoing Annual Testing)

Part B verification is the ongoing, recurring check that confirms the system continues to perform. It happens annually (or at whatever interval your operational policy defines) and confirms that nothing has deteriorated since the last check.

When it happens: At scheduled intervals throughout the system’s operational life.

What is tested:

• Air change rates
• Pressure differentials
• UCV airflow
• Filter integrity (where scheduled)
• Comparison against previous results

Who should do it: Again, independence is valuable here. If the company maintaining the system also verifies it, they are essentially marking their own homework. See our HTM 03-01 Part B verification service.

The Key Difference

Think of it simply:

• Part A asks: “Does this new system work as designed?”
• Part B asks: “Does this existing system still work as it did when validated?”

Both require competence, and both benefit from independence. If you would like to discuss either for your trust or facility, get in touch.